Constrain RaphaelJS print to boundaries and position - raphael

Question

I am looking for a more efficient way to constrain/set text in Raphael.
I have text that can be written in a box. That text should be centered (based on a number that could change if user wanted to shift text left/right) and the text cannot go beyond the boundaries of the paper.
This is what I do now and its not manageable performance wise
// Build a path
var path = this.paper.print(x, x, text, font, size, 'middle')
// Center line by getting bounding box and shifting to half of that
var bb = path.getBBox()
path.transform('...T' + [-bb.width / 2, 0])
// Compare paper size vs bb
// if it goes beyond I adjust X and Y accordingly and redo the above
So ideally I would like to predict the size of the text before it prints - I am not sure this is possible though as it is probably font dependent. I have looked for a command to contrain text but do not see one?
The other thought I had was to create some kind of shadow paper that does not print to screen and use that to determine size before I render to user. I am not sure where the lag is though - if it's in the screen rendering good but if its in the general logic of creating the svg then that wont help.
I'd appreciate suggestions

Answer 1

You can use opentype.js for measuring text, also you can get svg path by using Path.toPathData method. There is no need of cufon compiled js fonts.
For text measure, create a canvas element somewhere in your DOM.
<canvas id="canvas" style="display: none;"></canvas>
this function will load text and count width, height
function measureText(text, font_name, size) {
var dfd = $.Deferred();
opentype.load('/fonts/' + font_name + '.ttf', function (err, font) {
if (err) {
dfd.reject('Font is not loaded');
console.log('Could not load font: ' + err);
} else {
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height);
var tmp_path = font.getPath(text, 100, 100, size);
tmp_path.draw(ctx); // Draw path on the canvas
var ascent = 0;
var descent = 0;
var width = 0;
var scale = 1 / font.unitsPerEm * size;
var glyphs = font.stringToGlyphs(text_string);
for (var i = 0; i < glyphs.length; i++) {
var glyph = glyphs[i];
if (glyph.advanceWidth) {
width += glyph.advanceWidth * scale;
}
if (i < glyphs.length - 1) {
var kerningValue = font.getKerningValue(glyph, glyphs[i + 1]);
width += kerningValue * scale;
}
ascent = Math.max(ascent, glyph.yMax);
descent = Math.min(descent, glyph.yMin);
}
return dfd.resolve({
width: width,
height: ascent * scale,
actualBoundingBoxDescent: descent * scale,
fontBoundingBoxAscent: font.ascender * scale,
fontBoundingBoxDescent: font.descender * scale
});
}
});
return dfd.promise();
},
then use this function to get text dimensions:
$.when(measureText("ABCD", "arial", 48)).done(function(res) {
var height = res.height,
width = res.width;
...
});